12 JavaScript quirks

A core of JavaScript (the so-called “good parts”) is elegant, but that core is often obscured by quirks. This introduction is the first of a series of blog posts that looks at twelve common quirks and how to best deal with them:

1. Implicit conversion of values


2. Two “non-values” – undefined and null


3. Normal equality (==)


4. Unknown variable names create global variables


5. Parameter handling


6. The scope of variables


7. Inadvertent sharing of variables via closures


8. Array-like objects


9. Subtyping constructors


10. Reading and writing of properties


11. this in real functions


12. The for-in loop

A concluding post will cover ECMAScript 6 [1], which will eliminate most of the above quirks.

The series will provide a good overview of JavaScript. It is a translation of a previous blog post in German.
ECMAScript 5 will be used and a basic knowledge of JavaScript is required, but much will be explained. I will post one quirk per week.

Reference:

1. ECMAScript: ES.next versus ES 6 versus ES Harmony